OFL is saying you need to remove half of the water, two times a week.
One of those times just take out half of the water, no scrubbing or gravel cleaning necessary. The other time needs to include cleaning the gravel to remove old poop and food, either by rinsing the gravel or using a vacuum to suck up the poo and such (recommended.) These tank vacuums are extremely cheap and sold at places like petco for a few dollars.
When you do the second water change with gravel cleaning, it would be a good idea to rinse off the decor as well. If the plants are natural you do not need to rinse them, unless they have some algae or something, then you can just wipe them off with a damp paper towel.
OFL was explaining how nitrogen and other elements work together in the aquarium, which is a process called cycling. It is hard to cycle a tank under 10 gallons in my opinion and not really necessary. There is a sticky somewhere, I think under the Betta Care section that explains what cycling is and how to do it if you wish. It does get really technical!